Electronics can be divided into a simple hierarchy consisting of devices such as integrated circuit (IC) chips, packages, printed circuit boards (PCB), and systems. The package is the interface between an IC chip and a PCB. IC dies are made from semiconductor materials such as silicon. Dies are then assembled into packages such as quad flat packs (QFP), pin grid arrays (PGA), ball grid arrays (BGA), three dimensional integrated circuits (3DIC), wafer level packages (WLP), or package on package (PoP) devices, using wire bonding (WB), tape automated bonding (TAB), or flip chip (FC) bumping assembly techniques. The packaged die is then attached either directly to a PCB or to another substrate as the second level packaging.
3DIC technologies are known as vertical interconnect packaging technologies as they exploit the vertical dimension of the chip to reduce interconnect length and to achieve greater integration efficiency. The techniques for 3DIC package include wire-bonding, micro-bumps, through-vias, and more. A silicon interposer can be used to form a 3DIC package, where the interposer provides die-to-die interconnections for dies mounted on the interposer. For example, two dies may be bonded above each other by face-to-face or face-to-back stacking, with the lower die being coupled to the interposer by connectors such as micro-bumps. Alternatively, multiple dies may also be mounted in parallel above an interposer, and coupled to the interposer by connectors such as micro-bumps.
An inductor is a passive electrical component that stores energy in its magnetic field. Inductors are used extensively in analog circuits, signal processing systems, and wireless communication systems. Inductors in conjunction with capacitors and other components form circuits which can filter out specific signal frequencies. A transformer is a power converter that transfers electrical energy from one circuit to another. Two or more inductors with coupled magnetic flux form a transformer.
Performance of inductors and transformers formed on an IC chip may be increasingly limited by the shrinking device sizes, such as the shrinking thickness between metal layers of the chip, and the smaller areas occupied by the chip. Methods and apparatus are needed for inductors and transformers to improve the performance.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale.